Pilots Encounter Kasatochi Cloud
Aircraft Encounter the Ash Cloud from Kasatochi Volcano Eruption
Aug 18, 2008 Alexandra Matiella Novak
The eruption of Kasatochi Volcano, located in Alaska’s Aleutian Island Chain, has caused a series of ash cloud encounters with aircraft, according to pilot reports (PIREPS) gathered by the volcanological community. Most of these encounters happened in airspace over western Canada and were reported to the Montreal Volcano Ash Advisory Center.
Volcano Ash Advisory Centers (VAACs)
There are nine VAACs located all over the world and they are responsible for tracking ash clouds that can be hazardous to aircraft in a designated area. The other eight VAACs are located in Anchorage, Washington, D.C., Buenos Aires, London, Toulouse, Tokyo, Darwin and Wellington. These VAACs were established by the International Civil Aviation Organization upon recognizing that volcanic ash in the atmosphere is hazardous to aircraft and tracking of these clouds around the globe is required for safety.
VAACs use satellite data, transport models and observational data, such as pilot reports, to track volcanic ash clouds in the atmosphere and report their location and altitude to the aviation community. In most cases, accurate information about the location of ash clouds is communicated to pilots, who then navigate their plane in order to avoid an encounter. But sometimes, satellite tracking of a cloud is difficult or complex weather patterns make transport modeling inaccurate and a pilot will accidentally encounter an ash cloud.
Aircraft Encounter Kasatochi Ash Cloud
The low levels of ash in the Kasatochi Ash cloud made it difficult to track with satellites using the absorption features of ash, so scientists had to rely on the absorption features of sulfur dioxide to track the cloud. Scientists do not yet know what the minimum concentration of ash in a cloud has to be for it to be hazardous to aircraft, but even the smallest amount of ash can cause future mechanical problems for a plane.
Pilot reports of ash cloud encounters include the date, time, location and altitude of the encounter and any descriptions of the cloud. In the case of the Kasatochi cloud, pilots reported smelling sulfur and flying into a hazy, brown cloud. These encounters happened at flying levels as high as between 41,000 and 38,000 feet and as low as between 33,000 and 20,000 feet. These types of pilot reports are extremely significant and assist volcanologists in testing transport modeling and satellite sensing techniques of volcanic clouds in the atmosphere.
When a pilot encounters a volcanic cloud, they are trained to respond to the encounter by exiting the cloud as soon as possible. Frequently this means that the pilot must turn the plane around and fly in the opposite direction from which they came and in some cases a pilot may also descend to a different altitude if it is safe.
Sources:
Personal Communication, Dov Bensimon, Environment Canada
NOAA Satellite and Information Service
Alaska Volcano Observatory’s Kasatochi Activity Page
Kasatochi Volcano
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Worldwide Volcano Ash Advisor Centers (VAACs)
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